Ferrochromium-aluminum alloy



2,946,376 r 'rnnno'ennorn f'v Joseph H. Brenna n Niagara-Falls,-and Earlegk sannders,

Grand Island, N.Y., ass'gnors .t o .Union:anbide-Corporation, a corporationlo'flNew York No Drawing. Gontinuation 6f ti i plication Sir-ENO- 421,182, Apr.="5, 1954. l liis application Allin-#2991957, Ser..No.- 655,500

Tetanus. toms-:27

This invention relates to improved Eferroalloy, Qand more particularly concerns -anIimprovedi-ferrochromiumaluminum alloy, which .may be used I as an alloy addition,

sreacti'on and as an alloy :addition for atferr'ous melt. It

:rnust be non-reactive at ambient 'temperatures with the oxidant of the exothermic mixture. It should --be capable of reacting exothermically when added to .them'elt to produce a sufiicient quantity of heat to reduc'ef substantially the temperature drop :normally accompanying such addition. Itmustnot only bersuitableafor =useas an addition agent in melts requiring .the propagation of .heat, but as an eifective non-exothermic alloyaddition as well. 1

Aluminum possesses all of. the above attributes which are desirable in an alloy addition to be added to a' ferrous melt. Specifically, aluminum reacts exothermically with certainioxidiz'ing agents like sodiumnitiate or sodium bichromate-to generateramextremelylarge amount of .heat. With the aid of the heat releasedby the exothermic reaction, it is possible -to addproportionately largefquantities of alloying'm'at'erial tda'steel bath without rodueing any objectionable temperature drop in the"b'ath.

It is, therefore, an object of'the-present invention to provide a new and improved aluminum-bearing ferroalloy *that is suited for use as an alloy addition to' 'a' ferrous *m'lt.

Another-object of the invention is to provide a'h'ovel aluminum-bearing ferro'alloy which is suitable for use as a'reducing agent in an "exothermic reaction mixture.

Yet another object of thepresent invention 'is tofp'rovide a ferrous alloy containing aluminum andchromium in such correlated proportions that the alloyis suitable for use in either aluminurn bearing products or as a reducing agent in an exothermic reaction mixture.

The objects of the invention 'are achievedby forming an aluminum-bearing ferroalloy containing essentially chromium and iron constituents "for alloying in a'ferrous bath. Preferably, the alloy of the invention comprises aluminum, chromium, iron, optional amounts of silicon and carbon, and the usual impurities. In a preferred embodiment of the invention, the range of composition of the alloy should be Within the following limits.

Percent Aluminum to 85 Chromium '5 to 70 Iron 1.5 to 36 Silicon Up to 30 Carbon Up to 5 Small amounts of other elements may be introduced or may enter as incidental impurities.

ice

2 V V "Within the above range ther'atio of"ohromium"to ifon shouldbehetween'l25to1and4tol. I i 7 According "to the present invention,""ferrochfomilimaluminum alloys withinthe above com osition'range are useful as alloy additions for the production of aluminumb firigiteels," and referably asretlueing 'agntsimex- When used as'la-rflucin g 'ageiitfthe'aluniinum'con ent ref the instant alloy 'is' 'very powerfully-"exothermi' in fr'f'eactidn with "such csmmemy fused "oxidants *a's' sod um iiitrat orsodium bichromate. However, itfis to' be' po'iiit- *ed but that alloys of the above"'specified'range of cornposition' 'a'jrenot necessarily iresti'ict'e'dto oxidation of he aluminum when other'po'ssible'reflucingageritg like silicon f'andj carbon "are also "present, For example, in "exdthermic mixturs"employin'g"sodium nitrate a's'an o'xidant, successful restriction of the aluminum oxidation depends upon the presenceof a minimum of a stoi- --chiometric-quantit-y of aluminum for reaction with-all of the sodium nitrate. Otherwise the sodium nitrate preferentially reacts with the aluminum, silicon and carbon contents in the alloy in the order namedtuutil all of the sodiumnitrate isexhausted. Such a reaction has much less ie fiiciency because the heat producing 'capa'cities'of siliconand carbon are:approximatelyone halfto Y one-fourth that produced byQthe reaction of aluminum with sodium-nitrate. For thisreason an excess of alumi- -num-is usually preferred-in reactions with sodium-nitrate.

The-speeificexa-mple next to be referred to is illustrative of the selective type of exothermic reaction obtained when a-ferroch'romium-aluminum alloy of the present inventionis employed as areducing agentin anexothermic ereaction mixture. 7 p r I In a one-ton arc furnace heat, briquettes having a com position of 0.54% carbon, -4'.97% aluminum, 24 .60%

steelmelt. Beforethe briquettes were'added the steel-melt j ciontained 0.07% carbon, 0.04% silicon,-0.01}% aluminum,

:silicon and 8.0% "sodium nitrate wereiadded to;

remainderiron. After addin'g' the' above briquettesrthe composition of the steel melt was 0309% carbon, 1.10%

- silicon -and0.02% aluminum,=indicating-a 100%fcafrbon reeoveryv-fro'm the briquettes, =an-8'3 recoveryofisilicon and=a 4% aluminum recovery..

It :is desirable that the ferrochromium-aluminum 'alloy emb'odiediin the present-invention 'be easily reduced-no ,-,-powder form for obvious' 'metallur'gical reasons. 1X1- though the instant alloy compositionpossesses favorable ,jpulverulen't properties, it is alsosusceptible-of reduction 'to a fine particle size by a novel yet elfectivc method. This method consists in alloying aluminum with high carbon ferrochromium toxproduce an alloy in'which'much of the carbon is present as aluminum carbide, and leaching the resulting alloy with water. The aluminumwa'rbide of' the alloy reacts with thewater to form-hydrocarbon gas and aluminumhydrate. This reaction'causes the alloy to crumble and zreducesit t'o a fine poWder-andat the same time substantially lowers the'car bon content'of the alIoy.

The elfectiveness of this method of decarburization depends, of course, on the proportion of carbon present in the subject alloy as aluminum carbide. Investigation has shown that beginning at about 25% aluminum content, increasing proportions of the carbon present in the alloy are in the form of aluminum carbide. At aluminum levels of and over, practically all of the carbon in the alloy is present as aluminum carbide.

However, for reducing the alloy to a satisfactorily fine powder form, the alloy must have at least 50% aluminum. Best results are obtained when the aluminum content of the instant ferrochronnum-aluminum alloy is between 50% and by weight.

The following example illustrates the decarbonizatioa V 1 2,946,676 Patented July 26, 1960.-

end product desired determines the composition range of the alloy. Listed below in Table I are preferred composition ranges of fer-ro-chromium-aluminum alloys for use in exothermic mixes, which include alloys having either low carbon content, high carbon content, or high silicon content. The composition of these alloys lie in the broad range envisioned by this invention, but apply to a limited portion thereof.

Table I High Car- Low Car- High Silibon Alloy, bcn A110 con Alloy, percent percent percent Up to Up to 2 It is to be understood that modifications and variations may be effected without departing from the novel con cepts of the present invention.

This application is a continuation of application Serial No. 421,182, filed April 5, 1954, now abandoned.

What is claimed is:

1. In the manufacture of an alloy steel employing an exothermic reaction mixture as an additive material the improvement which comprises incorporating in said mixture an alloy having aluminum as an exothermic reducing agent therein, the alloy comprising from 5% to 85% aluminum, 5% to 70% chromium, silicon in an amount up to 30%, carbon in an amount up to 5% and the remainder iron, the ratio of said chromium to said iron being at least 1.5 to 1 and not more than 4 to 1.

2. In the manufacture of an alloy steel employing an exothermic reaction mixture as an additive material the improvement which comprises incorporating in said mixture an alloy having aluminum as an exothermic reducing agent therein, the alloy comprising from to 75% aluminum, 15 to 40% chromium, silicon in an amount up to 10%, carbon in an amount up to 2%, and the remainder iron.

3. In the manufacture of an alloy steel employing an exothermic reaction mixture as an'additive' material the improvement which comprises incorporating in said mixture an alloy having aluminum as an exothermic reduc ing agent therein, the alloy comprising from 5% to 25% aluminum, 35 to 55% chromium, silicon in an amount up to 30%; carbon-in an amount up to 2%, 'and the remainder iron. I V g V ;4. In-;themanufacture of an-jalloy steel employing an exothermic reaction as an additive material the improvement which comprises incorporating in said ,mixture, an alloy having aluminum as an exothermicre- .du'cingagent therein; thefalloy comprising from 5% to 25% aluminum, 45% to chromium, silicon in an amount up to 30%, carbon firom 0.2% to 5%, and the remainder iron.

5. A low carbon ferrochromium-aluminum alloy for admixture with an oxygen-containing oxidizing agent to provide an exothermic alloy addition mixture and "being characterized by the property of self-disintegration upon the addition of water, said alloy containing aluminum between 45% and chromium between 15% and 40%, silicon up to 10%, car-hon between 0.2% and 2%, and the remainder iron and incidental impurities.

6. A ferrochrom-ium-aluminum alloy for admixture with an oxygen-containing oxidizing agent to provide an exothermic alloy addition mixture comprising alumin between 5% and 25%, chromium between 35% and 55%, silicon up to 30%, carbon up to 2% and the remainder iron and incidental impurities, the ratio of said chromium to said iron being between 1.5 to 1.0 and 4.0 to 1.0.

7. A high carbon ferrochromium-aluminum alloy for admixture with an oxygen-containing oxidizing agent to provide an exothermic alloy addition mixture comprising aluminum between 5% and 25%, chromium between 45% and 70%, silicon up to 10%, carbon between 0.2% and 5% and the remainder iron and incidental impurities.

References Cited in the file of this patent UNITED STATES PATENTS 1,421,471 Heskett July 4," 1922 2,367,630 Udy Jan. 16, 1945 2,836,486 Brennan May 27, 1958 OTHER REFERENCES Kornilov: Iron Alloys, vol. I, Iron-Chromium- 

1. IN THE MANUFACTURE OF AN ALLOY STEEL EMPLOYING AN EXOTHERMIC REACTION MIXTURE AS AN ADDITIVE MATERIAL THE IMPROVEMENT WHICH COMPRISES INCORPORATING IN SAID MIXTURE AN ALLOY HAVING ALUMINUM AS AN EXOTHERMIC REDUCING AGENT THEREIN, THE ALLOY COMPRISING FROM 5% TO 85% ALUMINUM, 5% TO 70% CHROMIUM, SILICON IN AN AMOUNT UP TO 30%, CARBON IN AN AMOUNT UP TO 5% AND THE REMAINDER IRON, THE RATIO OF SAID CHROMIUM TO SAID IRON BEING AT LEAST 1.5 TO 1 AND NOT MORE THAN 4 TO
 1. 